1. Field of the Invention
The present invention is broadly concerned with an improved metallic baking pan particularly suited for combination baking of bread or other comestible products wherein a dough or batter is subjected to both conventional convection heating and microwave or rf radiation. More particularly, the invention pertains to a baking pan of this character, together with the combination baking method employing the pan, wherein the bottom and sidewall structure of the pan is apertured to permit entrance of microwave or rf radiation; in this fashion, crust formation can occur in the usual manner, while the microwave or rf radiation serves to completely bake the interior of the product. Properly sized and oriented apertures in the baking pan permit reduction in baking times, while nevertheless producing fully acceptable, baked final products.
2. Description of the Prior Art
The baking of bread or other food items may be thought of as an operation involving two very different physical reactions, occurring simultaneously. In the interior of a dough or batter, a number of physical and chemical changes occur that in their entirety can be described as cooking or gelatinization. Heat is required for these reactions, and they vary greatly depending upon the ingredients in the dough or batter. Simultaneously, a drying and crisping effect occurs on the surface of the product, leading to browning and crusting. Time honored baking processes involving differing time-temperature conditions have been developed for various types of final products, in order to create an effective matching of the complex simultaneous changes occurring during baking.
It has been suggested in the past to employ microwave or longer wavelength rf energy for baking purposes. The advantages of microwave use include lower utility costs, as well as reduced baking times. While in theory microwave baking is advantageous, on a practical level significant problems occur. For example, where microwave energy is used for bread baking, very little if any brown crust is formed, unless the baking operation is continued for relatively long periods, which effectively overcooks the interior of the bread. In short, microwave baking upsets the normal simultaneity of interior cooking and crust formation crucial to production of acceptable bread. Additionally, where metal baking pans are employed, the microwave energy can generally penetrate only from the open top of the pans, while being reflected from the metal pan walls. As a consequence, the top of the bread tends to overbake, while the interior and bottom part of the loaf is underbaked. Where use is made of glass or ceramic pans which are transparent to microwave energy, the crust is very pale, thin, wet and structurally weak.
It has also been suggested in the past to employ both conventional and microwave heating for baking purposes. This has been done simultaneously or serially, i.e., first applying microwave energy to obtain oven spring and setting of the bread structure, with subsequent finish baking using conventional heating to obtain crusting. Work that involved use of glass-type pans ("Pyrex" or "Corning Ware") was characterized by excessive collapse due to poor sidewall formation. Other work that involved baking in metal pans about 2-4 inches deep did not address the problems of poor penetration by 2450 MHz microwaves to the bottom of the dough, and excessive baking of the top.
The browning or crusting problem has also been addressed in the prior art through the use of microwave susceptors. These devices are generally made up of paper or synthetic resin substrates which are coated with a very thin metallic layer. This layer is intended to rapidly heat and reflect energy to the adjacent food surface, thereby browning the product. However, susceptors are prone to degradation at high temperatures, and can evolve dangerous or poisonous byproducts as a result. Furthermore, susceptors do not in practice give browning equivalent to that obtained when using conventional metallic baking pans.
There is accordingly a real and unsatisfied need in the art for an improved baking pan and method which combines the attributes of conventional metal baking pans while also permitting reduced time combination baking wherein the simultaneous processes of internal cooking and crust formation are properly coordinated.